Kirke's Science Project: Measuring Stress in Cranes
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| Kirke
Anderson Elsass and his Science Project in 2001 |
Kirke told Journey North: "One of my friends said, 'I can't believe you're going to be spending your summer researching crane poop.' It's been quite an experience." Kirke wanted a special science project. He won a grant to work with Dr. Julia Langenberg and Dr. Barry Hartup. Both are veterinarians with the whooping crane reintroduction project.
The Project
Whooping cranes, like those in the current migration study, react to stress
just as people would; but like us, they may not show any outward signs
of being stressed. Crane scientists wanted to find out how cranes would
be affected by the WCEP migration experiment. Would the birds be willing
to be near the ultralight aircraft so much? Could they deal with the stress
of it? Would they be willing to start migrating? They found that when
whooping cranes are stressed, they produce a specific hormone called corticosterone
(say COR ti KA ste rone).
Kirke explains: "Collecting feces is how scientists sample for levels of corticosterone, the avian stress hormone. They actually pick up the samples with things that look like tongue depressors. They have to freeze the samples within two hours of when they pick them up because the corticosterone is made of proteins that would fall apart just like meat that rots. We put the samples into these plastic bags called whirl-paks in the freezer. The samples go to San Diego. A woman at the Zoological Society of San Diego analyzes the samples.
What They're Finding
"We're getting correlations now between daily events and the corticosterone
levels," says Kirke. This information then allows scientists and
researchers to judge when a bird is likely to become stressed. Their greatest
concern is that if a a crane gets over-stressed, it can lead to its death.
The sandhill cranes were kind of a test to make sure this would work with whooping cranes, which are more fragile and also endangered. The team for the corticosterone studies also wanted to learn if fecal samples would indeed work to look at corticostone levels. Being able to correlate what they would have assumed to be stressful days and what turned out to actually BE stressful days is proving that fecal corticosterone levels work.
How They Find Out
Here's one example of what the scientists did: During the sandhill migration
they stopped at this place right by a highway with a lot of people and
coyotes in the area. They can look back on this and see that the cranes
had elevated levels when they were around the coyote. But if there's a
real stressul event and you take a fecal sample right then, the sample
may not yet show the increased level. We have to wait to be sure it gets
through the crane's body, which takes 2 to 5 hours. Then the corticosterone
shows up in their feces. Biologists feel pretty sure that this will also
be true for whooping cranes. The normal corticosterone level is 200 nanograms
per gram. Anything above is an elevated stress level."
With this knowledge, what will they do? "Try to eliminate stressful
events for the cranes in the reintroduction," explains Kirke. "Now
that they know that fecal samples work, they don't have to take blood
samples, which REALLY stresses cranes out."
An Awesome Experience
Kirke really liked working closely with the two veterinarians. He was
not allowed to pick up the feces himself because of rules about who can
come within eyesight of cranes, even wearing a costume. But Kirke says,
"The most awesome part was looking at last year's data and then being
able to pinpoint exact things that would have caused the stress to go
up. It was amazing that when they touch the birds, the birds would be
stressed out. The hormones showed they were. It's amazing that we can
find that out without talking to them! I was there the day the first chicks
arrived from Patuxent Wildlife Research Center in July 2001. Seeing a
new species come into our state was awesome too."
Try This! Journaling Questions
- Poop can
give some clues about the bird besides how much stress it's been having.
You know if a hummingbird has been drinking at a feeder with red color
added to the food because it keeps its color when it passes through
the bird. Bird rehabber Laura Erickson could often tell if a sick bird
had gone a while without food because their poop was green. The green
component was bile, which is usually broken down as it in turn breaks
down fat during digestion. If there is too little food, the unused bile
just goes straight through. What other clues do you think researchers
might be able to get about a bird's life from looking at or chemically
analyzing its droppings? Why is analyzing the poop of captive birds
simpler than analyzing that of wild birds?
- Do you think the stress of handling the cranes for their health check and banding is worth the information the scientists get? Explain your answer.
Exploring What Scientists Do!
- What did you learn from this story about how scientists work? What were two of the scientists' main questions? What was one of their hypotheses? How did they make sure their investigation was organized and "fair?" What did their data "tell" them? What will they do with the information they gained?
National Science Education Standards
- Science investigations involve asking and answering a question and comparing that to what scientists already know about the world.
- Scientists use different kinds of investigations depending on the questions they are trying to answer.
- Scientists develop explanations using observations (evidence) and what they already know about the world.
- Technology used to gather data enhances accuracy and allows scientists to analyze and quantify results of investigations.
- The behavior of individual organisms is influenced by internal cues (such as hunger) and by external cues (such as a change in the environment).
Journey
North is pleased to feature this educational adventure made possible by
the
Whooping Crane Eastern Partnership (WCEP).
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